Electric circuit breakers are commonly used to protect load or branch circuits in residential and commercial buildings against electrical overload and fault conditions. Example circuit breakers comprise a pair of separable contacts, a spring-operated mechanism for causing separation of the contacts, and a tripping mechanism that automatically releases the operating mechanism to break the connection between the contacts upon the occurrence of an electrical overload or fault condition.
Circuit breakers may be constructed with terminals to form an electrical connection with a load wire. Although the terminals may be mounted slightly below the surface of the circuit breaker's casing, it is possible that an operator could be severely burned or shocked if the operator accidentally touched the terminals while installing the circuit breaker. Further, adjacent circuit breakers could be short circuited if they were accidentally joined by a conducting material across the respective terminals. The terminals may also be subject to damage during the installation of other components near the circuit breaker.
Electrically insulated terminal shields have been used on circuit breakers, to cover the load terminal and protect an operator from inadvertently touching the terminals of the circuit breaker. When it has been desired to measure the load current passed by the circuit breaker, it has been the general practice to hang a current transformer sensor loosely somewhere along the load wire. Current transformer sensors are generally toroidally shaped coils that couple the magnetic field produced by the current conducted in the load wire. There have been efforts in the past to fasten the current transformer sensor to a chassis or to the wall of an electrical cabinet, but past mounting mechanisms required tools and special mounting lugs for installation and typically could only be installed at the time of the original assembly of the electrical components in the chassis or cabinet.